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Influence of Forearc Development on Sediment Routing: Detrital Zircon Provenance of Paleogene to Neogene Strata, East Coast of New Zealand

Abstract

The eastern continental margin of Zealandia, which has undergone rapid transformation in its tectonic regime throughout the late Cenozoic, provides an opportunity to study the interactions between active tectonics and source-to-sink sedimentation patterns. Detrital zircon U-Pb age distributions for 50 sandstone samples from the east coast of the North and South Island of New Zealand record the late Paleogene to Neogene sandstone provenance along the entire margin. Data span eight east–west transects, including three in the Raukumara, two in the Hawke's Bay, three in the Wairarapa, and two in the Marlborough Region. Age distributions are compared to published granitic basement ages and compiled detrital zircon ages of Permian through Lower Cretaceous metasedimentary terranes that can be distinguished based on detrital zircon age populations that are contemporaneous with depositional age. Preliminary marked trends suggest differences in sediment routing and presence of sediment barriers between the Raukumara and Wairarapa Region in the southern North Island. Detrital zircon age spectra from the Raukumara Region contain contemporaneous ages that are lacking farther south in the Wairarapa Region of the North Island, and provide possible constraints for early forearc configuration. Furthermore, there is a marked increase in sediment contribution derived from the Late Jurassic–Early Cretaceous Pahau terrane to the Wairarapa and Marlborough Regions during the middle Miocene, reflecting increased exhumation of local basement blocks associated with the development of the Alpine fault. Observed spatial and temporal trends have implications for understanding Cenozoic sediment dispersal to the margin and predicting reservoir distribution in the offshore East Coast and Pegasus basins.